Are you writing a series? That’s great because after readers finish a good book, they look forward to more from you. I’d like to share my tips.
Each book in a series must be a stand-alone. There can be an open-ended question, and I deliver the answer in the next book. Some authors who write a series have a mystery arching over the entire series that is answered in the final book.
If your series involves one character or a couple, write a happily for now ending rather than a happily ever after. My method is to change up the hero and heroine by writing a series with male cousins. This ensures some consistency across the series because the heroes are ex-military, honorable and courageous. As a writer of a series you need to keep track of the family tree, physical attributes, and locations. Consider using an Excel spreadsheet to maintain details. In my case I need to know ages of the characters and stomping grounds of their childhoods.
Consider what is logical. You’ve created a certain community and premise and must keep actions plausible. The technology your characters use reflects the world they live in. Their dialect must be consistent. Are they middle class or are they millionaires?
Have fun with your book series.